All tanks have stances and 1-2-3 combos. All melee have positionals and 1-2-3 combos. All healers have a HoT, a shield, an instant heal and an AoE, and deal damage by applying DoTs and casting a damage spell in between. If they change any of that then the new job will be different from existing ones.

RDM was a unique addition with its flexible casting rotation and the melee aspect. SAM could have been something new but ended up the same old 1-2-3 combos with positionals. A new tank and/or healer job should be next, and not for the reason of coaxing more people to play those roles but for the reason that players who enjoy those roles should receive something new at this point.

My personal wish is that a new healer job would only have physical melee attacks to deal damage and that a new tank would not have 1-2-3 combos. Transforming to a combat form would also be cool.